Early high speed tunnels encountered a phenomena similar to a sonic boom when trains entered the tunnel (and noise raced at the speed of sound to the other end). However, engineering solutions are now able to mitigate this phenomena. Residents should campaign to ensure that HS2 Ltd adopt such solutions and any technological improvements to those existing solutions, regardless of cost.

Even so, there will still be a long rumbling noise prior to the exit of the trains, and this (together with noise as the train eventually passes) will be a major concern. We have previously raised concerns of the effectiveness of 3 metre high barriers versus 5+ metre high trains, and will do so again.

Ground-borne vibration

A tunnel was not in the consultation proposals, and little information from government has so far been made available to residents. However we are able to access and share key research literature that the government is likely to refer to. This will include prominent work by academics David Thompson and Victor Krylov.

The government will point to the experience of High Speed 1 (formerly the Channel Tunnel Rail Link CTRL) for evidence that ground-borne vibration from high speed tunnels can be effectively mitigated. Such evidence will need to be balanced with independent evidence – including any views of residents along the existing HS1 route. Hillingdon Against HS2 will be seeking such information.

It should also be noted that the new route proposal has increased the speed design through Ruislip to 320kmh (previously 250kmh) and this is likely to increase the noise and vibration from the levels presented in the government consultation, particularly if trains are to exit the West Ruislip portal at maximum design speed.